Manufacture of artificial filaments



Patented Mar. 29, 1938 UNITED STATES MANUFACTURE OF ARTIFICIAL FILAMENTSWilliam Alexander Dickie, Spondon, near Derby, England, assignor toCelanese Corporation of America, a corporation of Delaware No Drawing.Application July 21, 1933, Serial 12 Claims.

This invention relates to improvements in the production and treatmentof artificial filaments, threads, yarns, ribbons and the like containingorganic derivatives of cellulose, and particularly to the production ofartificial materials by wet spinning processes and to the treatment ofartificial materials obtained by any dry or wet spinning process. 1

U. S. Patents Nos. 1,465,994 and 1,467,493 delO scribe the use, in theproduction of artificial filaments and the like by Wet spinningprocesses, of aqueous coagulating baths containing solvents or latentsolvents for cellulose acetate, for example thiocyanates, zinc chloride,diacetone al- 15 cohol, acetic acid and other organic or inorganicsubstances. British Patent No. 340,324 describes the coagulation ofsolutions containing organic derivatives of cellulose by means of mediacontaining solvents for the cellulose derivative in relatively highconcentration, and also processes in which the solvent is incorporatedin the spinning solution itself either Wholly or in part in place of thesolvent in the coagulating bath, and with the treatment of the productsimmediately after coagulation so as to bring them into a plastic state.British Patent No. 340,324 also describes the coagulation of solutionsof organic derivatives of cellulose by means of coagulating bathscontaining aliphatic esters or partial ethers of polyhydric alcohols,While British Patent No. 380,819 carries out the coagulation of suchsolutions by means of coagulating media of high solvent power containinglower aliphatic acids and high boiling solvents.

Again, in U. S. Patent No. 1,709,470 there is described the stretchingof cellulose acetate silk filaments beyond their elastic limit at anystage of their manufacture after the silk is in the fully set andfinished condition in order to improve .11 their resistance todelustring by hot aqueous liquors, and it is mentioned that assistingagents, for example, acetone, ethyl alcohol, formaldehyde and glycerine,may be employed to assist the stretching operation. Further, in Brit ishPatent No. 323,790 the stretching of artificial filaments and the likecontaining organic derivatives of cellulose during their travel from onepoint to another in order to increase their tensile strength isdescribed, and in this case also,

no suitable assisting agents may be used to facilitate the stretching.French Patent No. 663,743 describes p-rocesses for improving the tensilestrength of materials containing organic derivatives of cellulose inwhich they are treated with .35 relatively high concentrations oforganic solvents, such treatment being, if desired, carried out inconjunction with a stretching operation. The stretching of artificialfilaments and the like in stages is described in British Patent No.370,430, 60 while British Patent No. 371,461 describes In Great BritainAugust 11,

stretching processes applied to artificial filaments, threads, yarns andthe like in warp form. In these cases also the stretching operation maybe assisted by means of solvents for the organic derivative ofcellulose.

I have now discovered that the coagulation of solutions of organicderivatives of cellulose and the stretching of artificial materialscontaining such derivatives, for example by any of the processesdescribed in the above specifications, may be assisted by the use ofliquid organic solvents for the cellulose derivative, preferably used insolutions of relatively high concentration, in conjunction with solidsubstances, which may be organic or inorganic and which have at least aslight solvent or swelling action on the cellulose derivative.

The organic solvents and solid substances are preferably employed insolution in non-solvent diluents but they may be applied in any othersuitable manner. Thus, the solvent and solid substance may be appliedtogether dissolved in a non-solvent for the cellulose derivative, whichnon-solvent will act as a diluent, or, where the solid substance issoluble in the organic solvent, a solution of the solid substance in theorganic solvent alone may be directly employed if applied under suchconditions that too strong a solvent action on the cellulose derivativedoes not result.

As stated above, the solid substances employed may be either organic orinorganic in nature and among suitable compounds may be mentioned ureaand substitution derivatives thereof, for example s-diethyl urea,as-diethyl diphenyl urea, s-diethyl diphenyl urea, tetraphenyl urea,thiourea, s-dimethyl thiourea, guanidine and monomethyl guanidine. Inaddition thiocyanates, e. g. sodium and. potassium thiocyanates, andzinc chloride may be employed.

The organic solvents employed may be any of those mentioned in the abovespecifications and may be of low, medium or high boiling point. Suitablesolvents are acetone, methylene ethylene oxide, ethyl lactate, diethyltartrate, dioxane, diacetone alcohol, 1.4-oxanone and the ethers, estersand ether-esters of polyhydroxy alcohols, e. g. mono-, diandtri-acetins, glycol mono acetate and methyl glycol mono acetate. Suchsolvents may also be employed in preparing spinning solutions from whichthe materials are prepared. The solvents and solid substances arepreferably applied in solution in diluents having themselves no solventor swelling action on the organic derivatives of cellulose. Suchdiluents may be water or other hydroxy bodies, for example ethyl andother monoor poly-hydroxy alcohols or hydrocarbons, for example benzene,toluene or other coal tar hydrocarbons, gasoline, kerosene or otherpetroleum hydrocarbons and chlorinated compounds, for example carbontetrachloride.

When the process of the present invention ,is applied in the coagulationof solutions of organic derivatives of cellulose such solutions may beextruded into a bath cOntaining a solution of the solvent for thecellulose derivative and the solid substance, or one or both of thecompounds, or a portion thereof, may be contained in the spinningsolution or in a subsequent treatment bath|. Preferably the materialsare stretched continuously with their production by such wet spinningmethods and in this case means may be adopted to restrict the tensionapplied to the materials, for example to prevent the stretching tensionrunning back as far as the spinning jets as described in U. S. PatentNo. 2,025,730. Furthermore, if desired, the stretching of the materialsmay be effected or assisted by means of a moving body of coagulatingliquid as described in British Patent No. 375,424. Where the presentinvention is applied to the production of films, foils, sheets and thelike the materials may be subjected to a longitudinal and/or transversestretch as described in British Patent No. 400,597. Again, in theproduction of the materials whether in the form of laments, yarns andthe like or of films, foils and the like the coagulating bath maycontain an organic solvent which is the same as that employed in thespinning solution from which the materials are produced. Such processes.are described, for example, in British Patents Nos. 405,676, and405,619.

In the case of stretching artificial materials the solvents and solidsubstances used according to the present invention are preferablyapplied by passing the artificial materials through a bath containingthe same, though, if desired, they may be applied by other methods, forexample by spraying, or by passing the materials over wicks, rollers orthe like impregnated with solutions containing the media. Theapplication of the softening agents may take place prior to or duringeach stage of the stretching and, if desired, the materials may besubjected to a plurality of softening treatments of diiferent strengthsas described in French Patent No. 740,775. As stated above stretchingmay, if desired, be carried out in a number of stages and preferablyduring such multi-stage stretching the softening agents are not removedbetween the stages of stretching. Such processes are described, forexample, in British Patent No. 370,430.

The stretching operation may be carried out upon the materials in anyconvenient form.

Thus, for example, hanks may be soaked in a solution containing theliquid organic solvent and the solid substance and then stretched.Again, the process may be carried out on the filaments or yarns duringtheir travel from one point to another, for example continuously withtheir production by dry or wet'spinning processes, or during a bobbin tobobbin rewinding operation as described in British Patent No. 323,790.It may very advantageously be applied to the stretching of a number ofthreads or yarns arranged as a warp as described in British Patent No.371,461. Thus, for example, threads taken from a creel of bobbins may bearranged in warp formation and led through a bath containing the organicsolvent and the solid substance, or the threads on bobbins may bepartially softened by ore-soaking the bobbins in a bath comprising theorganic solvent and the solid substance and the threads from suchbobbins arranged in warp formation and led through a further bathcontaining the organic solvent and the solid substance. After thematerials have been softened by either of the above desoribed'methodsthe stretch maybe applied to the warp as a whole. Where the stretchingoperation is carried out upon films, foils, sheets. and the like, thematerials may be subjected to a longitudinal and transverse stretchsimultaneously as described in British Patent No. 400,589.

Where the application of the softening agent and the stretching iscarried out as a continuous process the stretching force may be applieddirectly to the softened part of the materials or it may be appliedthereto after the softening agent has been removed and even afterdrying, since the tension may be allowed to run back to the softenedportion of the materials. Advantageously means may be adopted to preventthe whole or part of the stretching tension acting upon the unsoftenedor incompletely softened portion of the filaments. Such processes aredescribed, for example, in French Patent No. 755,621.

As stated above, the solvents employed according to the presentinvention are preferably applied in relatively high concentration, forexample concentrations of from 25 to 65%, while the concentration of thesolid substance will in general be lower, for example from 2 to 5 or ormore. Since the solid substances employed according to the presentinvention have themselves some solvent or swelling action upon theorganic deriva tive of cellulose, the proportion of liquid organicsolvent employed will in general vary inversely as the proportion ofsolid substance.

7 The treatment of the materials with the organic solvent in conjunctionwith the solid substance may be carried out at any suitabletemperatures, but preferably is effected at atmospheric temperature. Theconcentration necessary to effect a high degree of softening of thematerials which is valuable in obtaining high degrees of stretching,will in general vary with the temperature, lower concentrations beingemployed with higher temperatures.

if desired, filaments, threads, yarns and the like of cellulose estersmay be treated continuously with their stretching by the process of thepresent invention with saponifying agents so as to obtain either aproduct which consists partly of cellulose ester and partly ofregenerated cellulose, for example a superficially saponified product,or which consists of a cellulose ester of a lower ester content, orwhich is substantially regenerated cellulose. By this means products maybe produced having affinity for cotton dyestuffs and a very high tensilestrength. The saponification may be carried out with any suitablesaponifying agent, for example aqueous caustic soda, caustic potash,trisodium phosphate and the like to which. it is preferable to addsodium acetate or soaps or like buffer substances. Alcoholic solutionsmay be employed, for example ethyl alcohol solutions of caustic soda orcaustic potash or solutions of those substances in methyl alcohol or analcohol higher than ethyl alcohol or a glycol, glycerine or otherpolyhydric alcohol. Such processes are described, for example, inBritish Patent No. 402,104. Aqueous saponifying treatments may becarried out in the presence of lime or similar agents as described inBritish Patent No. 402,105. It is advantageous to carry out suchsaponifying treatments upon the materials whilst they are in Warpformation.

The organic solvents and solid substances with which the materials aretreated according to the present invention may be allowed to remain inthe materials while they are subjected to the saponifying treatment, ormay be removed therefrom before such treatment. The organic solvents andsolid substances used, however, may assist in the saponifying treatment.

The materials may be subjected to any other further treatment in orderto modify their properties, for example to alter their lustre and theymay carry with them the solvents or solid substances employed accordingto the present invention, which may assist in such after-treatmentprocesses. Again, effects may be produced by the local application ofthe solvents and/r solid substances of the present invention followed byor simultaneously with a stretching process. Thus, the solvent and/ orsolid substance may be locally applied to the materials and thematerials then subjected to a stretching treatment. It is then foundthat the stretching is substantially confined tothe softened parts ofthe filaments or other products. treated with the softening agents andsubjected to a process of stretching in which the tension is appliedintermittently. Means whereby differentially strained yarns may beproduced are described in U. S. Patent No. 2,004,139. Furthermore,materials which have thus been differentially stretched along theirlength may be treated with saponifying agents to obtain differentialsaponifying eifects along their length as described in British PatentNo. 400,938, and may, moreover, be subjected to suitable delustringtreatments which will produce difierential delustred effects along theirlength as described in British Patent No. 400,946.

After a stretching operation the materials may be subjected to ashrinking operation to improve their extension. Such shrinking may beeffected in the presence of the organic solvent and the solid substanceemployed in the stretching operation or may be effected with the aid ofother solvents or strong swelling agents, for example acetic acid,formic acid, lactic acid, diaoetone alcohol, acetone, dioxane, methyleneethylene oxide, 1-4-oxanone and the monoesters, di-esters or etheresters of polyolefine glycols, e. g. glycol mono acetate and ethylglycol mono acetate, methylene chloride, dichlorethylene, ethyl lactate,and diethyl tartrate. Suitable shrinking processes are described, forexample in British Patent No. 389,823. Again, the materials may besubjected to a shrinking operation prior to stretching as described inBritish Patent No. 403,106.

After the process of the present invention the organic solvent and thesolid substance employed may be removed by any suitable means. In orderto preserve the lustre of the materials it is desirable, especially ifthe agents have been applied in high concentrations, to remove theagents by washing with water, or other liquid, containing either thesame agent or another solvent or softening agent in lower concentrationthan that employed in the softening treatment, or to wash with liquidscontaining salts or other agents adapted to prevent or diminish loss oflustre. It is particularly useful to wash the materials with mediacomprising solvents for the materials which are less volatile than thesolvents which are to be removed. Again, the softening liquid or aportion thereof may itself be employed for washing the materials, forexample as described in Again, the materials may be.

British Patent No. 401,679. Advantageously the materials are subjectedto two or more washings with such solutions of successively decreasingconcentrations. The materials may be dried whilst they are under tensionor in the absence of tension and the drying operation may be carried outwhen all the softening agent has been removed from the materials or whenthe materials still contain a portion of the softening agent. Thus,drying may be effected under such conditions that shrinkage isprevented, or under such conditions that a desired amount of shrinkageis allowed to take place. Where the solid substance is not deleteriousto the materials, and where it is of advantage to leave it in or uponthe materials, the organic solvent may simply be evaporated from thematerials, leaving the solid substance in situ.

The following examples serve to illustrate the invention, but they donot, of course, limit it in any way:

Example 1 A 25% solution of cellulose acetate is spun through orifices.08 mm. diameter into a bath containing 5% by weight of potassiumthiocyanate, 45% by weight of diacetone alcohol and 50% by weight ofwater. After a travel through this bath of a distance of 8-l0 inches thefilaments are withdrawn by means of a draw roller at a speed of 50metres per minute. After removal of the solvent and the solid substanceby a suitable washing operation, the materials are dried and wound ortwisted and wound.

Example 2 The process described in Example 1 is carried out except thatthe solution of cellulose acetate is extruded into an aqueous bathcontaining 2.5% by weight of urea and 47.5% by weight of ethyl lactate.In this process the urea not only assists in the coagulation of thefilaments, but also assists in preventing the coagulating bath frombecoming acid.

In each of the above examples the ratio of the peripheral speed of thedraw roller to the rate of extrusion may be such that the filaments arestretched, e. g. by 200%-300% or more.

Example 3 A number of cellulose acetate threads are led from a creel ofbobbins through a reed or other spacing device and in the form of a warpare led under a feed roller and immersed into an aqueous bath containing2.53.5% by weight of urea and 46.5-47.5% by weight of dioxane. After atravel of between 80 and 100 feet the threads are withdrawn from thebath through another reed by means of a stretching roller which rotatesat such a speed as to effect a stretch of about 400 to 500% on theoriginal length of the threads. The warp of threads issuing from thebath is led through suitable washing baths and the threads are thendried and wound in any suitable manner.

The process of the present invention is of particular value inconnection with artificial filaments, threads, ribbons and the likecontaining cellulose acetate,but it may also be applied to other organicesters or mixed esters of cellulose, for example cellulose formate,propionate, butyrate and nitroacetate, methyl, butyl, benzyl and othercellulose others or mixed ethers and cellulose ether-esters, for exampleoxyethyl cellulose acetate and ethyl cellulose acetate.

What I claim and desire to secure by Letters Patent is:-

1. In the manufacture of artificial filaments, yarns, threads, ribbons,foils, films and the like from solutions of organic derivatives ofcellulose, the steps of extruding a solution of an organic derivative ofcellulose through a suitable shaping device into a coagulating mediumcontaining in a non-solvent diluent a concentration of 25 to 65% of aliquid organic solvent for the cellulose derivative and a proportion of2 to 10% of the medium of an organic substance which is normally solidand has at least a slight swelling action on the cellulose derivative,and subjecting the materials to a stretching operation.

2. In the manufacture of artificial filaments, yarns, threads, ribbons,foils, films and the like from solutions of cellulose acetate, the stepsof extruding a solution of cellulose acetate through a suitable shapingdevice into an aqueous coagulating medium containing a concentration of25 to 65% of a liquid organic solvent for the cellulose acetate and aproportion of 2 to 10% of the medium of a substance selected from thegroup consisting of urea and its solid substitution derivatives, whichhas at least a slight swelling action on the cellulose acetate, andsubjecting the materials to a stretching operation.

3. In the manufacture of artificial filaments, yarns, threads, ribbons,foils, films and the like from solutions of organic derivatives ofcellulose, the steps of extruding a solution of an organic derivative ofcellulose into an aqueous coagulating medium containing a concentrationof 25 to 65% of a liquid organic solvent for the cellulose derivativeand a proportion of 2 to 10% of the medium of a substance selected fromthe group consisting of urea and its solid substitution derivativeswhich has at least a slight swelling action on the cellulose derivative,and subjecting the materials to a stretching operation.

4. In the manufacture of artificial filaments, yarns, threads, ribbons,foils, films and the like from solutions of cellulose acetate, the stepsof extruding a solution of cellulose acetate through a suitable shapingdevice into an. aqueous coagulating medium containing from 25-65% of aliquid organic solvent for the cellulose acetate and from 2-10% of urea,and subjecting the materials to a stretching operation.

5. In the treatment of artificial filaments, yarns, threads, ribbons,foils, films and like products containing organic derivatives ofcellulose, the steps of softening the products by the action of a liquidmedium containing in a non-solvent diluent a concentration of 25 to 65%of a liquid organic solvent for the cellulose derivative and aproportion of 2 to 10% of the medium of an organic substance which isnormally solid and has at least a slight swelling action on thecellulose derivative, and subjecting the products to a stretchingoperation.

6. In the treatment of artificial filaments, threads, yarns, ribbons,foils, films and like products containing cellulose acetate, the stepsof softening the products by the action of an aqueous medium containinga concentration of 25 to 65% of a liquid organic solvent for thecellulose acetate and aproportion of 2 to 10% of the medium of asubstance selected from the group consisting of urea and its solidsubstitution derivatives, which has at least a slight swelling action onthe cellulose acetate, and subjecting the products to a stretchingoperation.

'7. In the treatment of. artificial filaments, yarns, threads and likeproducts containing cellulose acetate, the steps of softening a numberof the products arranged in warp formation by the action of a liquidmedium containing in a non-solvent diluent a concentration of 25 to 65%ofva liquid organic solvent for the cellulose acetate and a proportionof 2 to 10% of the medium of a substance selected from the groupconsisting of urea and its solid substitution derivatives, which has atleast a slight swelling action on the cellulose acetate, and subjectingthe products to a stretching operation.

8. In the treatment of artificial filaments, threads, yarns, ribbons,foils, films and like products containing organic derivatives ofcellulose, the steps of softening the products by the action of anaqueous coagulating medium containing from 25-65% of a liquid organicsolvent for the cellulose derivative and a proportion of 2 to 10% of themedium of a substance selected from the group consisting of urea and itssolid substitution derivatives which has at least a slight swellingaction on the cellulose derivative, and subjecting the products to astretching operation.

9. In the treatment of, artificial filaments, threads, yarns, ribbons,foils, films and like products containing cellulose acetate, the stepsof softening the products by the action of an aqueous medium containingfrom 25-65% of a liquid organic solvent for the cellulose acetate andfrom 2-10% of urea, and subjecting the products to a stretchingoperation.

10. In the manufacture of artificial filaments, yarns, threads, ribbons,foils, films and the like from. solutions of organic derivatives ofvcellulose, the steps of subjecting the shaped materials to the action ofa liquid medium containing in a non-solvent diluent a concentration of25 to 65% of a liquid organic solvent for the cellulose derivative and aproportion not more than of the order of 10% of the medium of asubstance selected from the group consisting of urea and its solidsubstitution derivatives which has at least a slight swelling action onthe cellulose derivative, and subjecting the materials to a stretchingoperation. 7

11. In the manufacture of. artificial filaments, yarns, threads,ribbons, foils, films and the like from solutions of organic derivativesof cellulose, the steps of extruding a solution of an organic derivativeof cellulose through a suitable shaping device into a coagulating mediumcontaining in a non-solvent diluent a concentration of 25 to 65% of aliquid organic solvent for the cellulose derivative and a proportion of2 to 10% of the medium of a substance selected from the group consistingof urea and its solid substitution derivatives which has at least aslight swelling action on the cellulose derivative, and subjecting thematerials to a stretching operation.

12. In the treatment of artificial filaments, yarns, threads, ribbons,foils, films and like products containing organic derivatives ofcellulose, the steps of softening the products by the action of a liquidmedium containing in a non-solvent diluent a concentration of 25 to 65%of a liquid organic solvent for the cellulose derivative and aproportion of 2 to 10% of the medium of. a substance selected from thegroup consisting of urea and its solid substitution derivatives whichhas at least a slight swelling action on the cellulose derivative, andsubjecting the products to a stretching operation.

WILLIAM ALEXANDER DICKIE.

